In radical chlorination of alkanes, non-equivalent hydrogens react with chlorine

Question

In radical chlorination of alkanes, non-equivalent hydrogens react with chlorine atoms at different rates. At 35 °C, primary, secondary, and tertiary C-H bonds react at relative rates of 1 : 3.9 : 5.2 respectively.

These are conditions of kinetic control where product ratios are determined by relative rates of formation. For example, if A is formed twice as fast as B, the A:B product ratio will be 2.

Consider chlorination of the alkane below at 35 °C.

1.Specify the most reactive C-H bond(s), a-c.
Two non-equivalent C-H bonds of comparable reactivity should be separated by commas, i.e. a,c.

2.Specify the site of chlorination in the major monochloro substitution product, a-c.
Two products that form in comparable quantities should be separated by commas, i.e. a,c

Explanation / Answer

As we know that chlorination occurs at the carbon which is most active, which is the tertiary carbon.

1.

In a,b, and c;

a is secondary, b is tertiary and c is primary carbon centre. Those C-H bonds are most activewhich have the highest electron charge density. Tertiary carbon has the most electron density. So b has the most reactive C-H bond.

2.

The site for monochlorination will be the most reactive site, i.e the tertiary carbon site which is b.

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.